Face-on galaxies

view Abstract Citations (145) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Twenty-one centimeter line widths of galaxies. Roberts, M. S. Abstract Results are presented for a simulation of 21-cm velocity profiles of spiral galaxies. The relation between profile widths and rotation curves is examined, and observed line widths for nearly 500 galaxies are analyzed. It is shown that because of a relation between intrinsic line width and absolute magnitude, the former, though independent of distance, is subject to the same selection effects as any distance-dependent property derived from a magnitude-limited sample. The dependence of intrinsic line width on galaxy type is also investigated. It is found that for samples of the same absolute magnitude, late-type galaxies have systematically smaller intrinsic line widths than early-type systems. Publication: The Astronomical Journal Pub Date: September 1978 DOI: 10.1086/112287 Bibcode: 1978AJ.....83.1026R Keywords: Galactic Rotation; H Lines; Radial Velocity; Spectral Line Width; Spiral Galaxies; Centimeter Waves; Distance; Galactic Evolution; Galactic Structure; Magnitude; Mass Distribution; Radio Astronomy; Velocity Distribution; Astrophysics; Galaxies:Neutral Hydrogen; Galaxies:Rotation full text sources ADS | data products SIMBAD (8) NED (8)

view Abstract Citations (77) References (40) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Internal Kinematics of Spiral Galaxies: Gas and Stellar Rotation Curves and Dispersion Profiles Fillmore, J. A. ; Boroson, T. A. ; Dressler, A. Abstract Emission- and absorption-line observations of six moderately inclined spiral galaxies are presented. The mean rotation and velocity dispersion for the gas and the stars have been measured. Two component mass models are fitted to surface brightness measurements are used to fit kinematic models to the velocity data. Models with constant mass-to-light ratios and isotropic velocity dispersions roughly fit the inner regions of spiral galaxies with three caveats: (1) several galaxies show significant kinematic differences between the two sides of the galaxy. While the differences might be caused by nonaxisymmetric potentials, variations in the line-of-sight extinction are a more likely cause; (2) the inner portion (R less than of equal to 1 kpc) of the emission-line (gas) rotation curve falls below the predicted circular velocity. Because the model circular velocities are computed from the observed stellar velocities, variations in the total mass-to-light ratio will not change the model values. It is noted that gas lost from bulge giants (planetary nebulae) will have a significant noncircular velocity component. It is shown that these emitted clouds live a sufficient time to explain the lower-than-circular velocity of the emission-line rotation curves; Some of the bulges are flatter than one would expect from their rotation rate, assuming isotropic random motions, but this additional flattening could be caused by the disk potential. Publication: The Astrophysical Journal Pub Date: March 1986 DOI: 10.1086/163984 Bibcode: 1986ApJ...302..208F Keywords: Galactic Structure; Spiral Galaxies; Stellar Rotation; Absorption Spectra; Emission Spectra; Kinematics; Line Spectra; Mass To Light Ratios; Radial Velocity; Tables (Data); Astrophysics; GALAXIES: INTERNAL MOTIONS; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (6) NED (6)

We report that MONDian dark matter (MDM) is a new form of dark matter quantum that naturally accounts for Milgrom's scaling, usually associated with modified Newtonian dynamics (MOND), and theoretically behaves like cold dark matter (CDM) at cluster and cosmic scales. In this paper, we provide the first observational test of MDM by fitting rotation curves to a sample of 30 local spiral galaxies (z approximately 0.003). For comparison, we also fit the galactic rotation curves using MOND, and CDM. We find that all three models fit the data well. The rotation curves predicted by MDM and MOND are virtually indistinguishable over the range of observed radii (~1 to 30 kpc). The best-fit MDM and CDM density profiles are compared. We also compare with MDM the dark matter density profiles arising from MOND if Milgrom's formula is interpreted as Newtonian gravity with an extra source term instead of as a modification of inertia. We find that discrepancies between MDM and MOND will occur near the center of a typical spiral galaxy. In these regions, instead of continuing to rise sharply, the MDM mass density turns over and drops as we approach the center of the galaxy. Our results show that MDM, which restricts the nature of the dark matter quantum by accounting for Milgrom's scaling, accurately reproduces observed rotation curves.

A better understanding of the formation of mass structures in the universe\ncan be obtained by determining the amount and distribution of dark and luminous\nmatter in spiral galaxies. To investigate such matters a sample of 12 galaxies,\nmost with accurate distances, has been composed of which the luminosities are\ndistributed regularly over a range spanning 2.5 orders of magnitude. Of the\nobserved high quality and extended rotation curves of these galaxies\ndecompositions have been made, for four different schemes, each with two free\nparameters. For a "maximum disc fit" the rotation curves can be well matched,\nyet a large range of mass-to-light ratios for the individual galaxies is\nrequired. For the alternative gravitational theory of MOND the rotation curves\ncan be explained if the fundamental parameter associated with MOND is allowed\nas a free parameter. Fixing that parameter leads to a disagreement between the\npredicted and observed rotation curves for a few galaxies. When cosmologically\nmotivated NFW dark matter halos are assumed, the rotation curves for the least\nmassive galaxies can, by no means, be reproduced; cores are definitively\npreferred over cusps. Finally, decompositions have been made for a pseudo\nisothermal halo combined with a universal M/L ratio. For the latter, the light\nof each galactic disc and bulge has been corrected for extinction and has been\nscaled by the effect of stellar population. This scheme can successfully\nexplain the observed rotations and leads to sub maximum disc mass\ncontributions. Properties of the resulting dark matter halos are described and\na ratio between dark and baryonic mass of approximately 9 for the least, and of\napproximately 5, for the most luminous galaxies has been determined, at the\noutermost measured rotation.\n

view Abstract Citations (125) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The gas distribution in the central region of the Galaxy. I. Atomic hydrogen. Burton, W. B. ; Liszt, H. S. Abstract A phenomenological model that accounts in a simple and coherent manner for many of the anomalous phenomena observed toward the galactic nucleus is developed. This model for the inner-Galaxy gas distribution invokes rotation and outward flow of comparable magnitude in an inclined thin disk, as well as gas density variation only with distance from the mean plane of the disk and axisymmetric velocity fields. The model is used to generate synthetic H I profiles for comparison with observations. Moment maps of integrated H I intensity as they appear projected onto the plane of the sky are examined along with intensity contours in an (l, v) map constructed along the major axis of the fundamental gas distribution, the observed and predicted behavior in 10 representative (l, v) maps, and the same behavior in four (b, v) maps. It is shown that the appearance of apparently isolated and anomalous spectral features is a consequence of transforming the properties of the tilted disk into the observed coordinates and intensities Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/156547 Bibcode: 1978ApJ...225..815B Keywords: Astronomical Models; Density Distribution; Galactic Nuclei; Galactic Structure; Gas Density; Interstellar Gas; Milky Way Galaxy; Cosmic Gases; Disks (Shapes); Emission Spectra; Galactic Rotation; Hydrogen Atoms; Hydrogen Clouds; Astrophysics; Galactic Center:Neutral Hydrogen; Galactic Structure; Galaxy:Internal Motions; Galaxy: 21 cm Radiation full text sources ADS |

view Abstract Citations (46) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Integrated magnItudes and mean colors of DDO dwarf galaxies in the UBV system. II. Distances, luminosities, and HI properties. de Vaucouleurs, G. ; de Vaucouleurs, A. ; Buta, R. Abstract An analysis of the properties of the DDO magellanic irregular "dwarf" galaxies for which U, B, V photometry was reported in Paper I leads to the following conclusions: (1) The mean effective surface brightness (m'e)0 varies with zenith distance as expected from the dependence on sec z of atmospheric extinction and sky brightness. (2) The mean surface brightness is independent of distance modulus (25 < μ0 < 33). (3) The mean absolute magnitude M0T is brighter than average (and the mean effective linear diameter larger) south of +10° declination (dwarfs fainter than -15 are missing) and fainter near the zenith at Palomar. There is a curious near absence of DDO objects in the zone +20° < δ < + 30°. The range of absolute magnitudes (-19 < M0T < -12) is largest north of +60° declination. (4) The mean corrected effective color index (U - V )0e is independent of absolute magnitude at M 0T < -15, but fainter systems tend to be bluer. (5) The mean absolute magnitude M0T is correlated with distance modulus at μ0 > 28; we confirm that the DDO sample is not restricted to dwarf systems and includes galaxies as bright as M0T <∼ -18 at μ0 > 30.(6) We confirm also that the luminosity class L and luminosity index Λ are not valid indicators of absolute magnitude for late-type systems beyond μ0 ≃ (Δ = 4 Mpc). (7) Effective linear diameter and absolute magnitude are highly correlated (i.e., mean surface brightness is not a distance indicator). (8) Apparent magnitude and 21-cm line flux are loosely correlated, but there is a large range of HI index (hydrogen/luminosity ratio) among the DDO objects at a given Hubble type (Sd to Im). (9) The relative excess or deficiency in hydrogen/luminosity ratio is uncorrelated with mean effective surface brightness (except for selection effects). (10) The hydrogen/luminosity ratio residuals (at a given type) are loosely correlated with color residuals: DDO objects richer than average in neutral hydrogen tend to be bluer in (U - V )0e (11) The necessity of correcting H I linewidths for velocity dispersion is once again demonstrated by the conspicuous departure from linearity of the Tully-Fisher relation based on raw linewidths. Correction for turbulent motions restores the linearity of the relation. For want of reliable inclination estimates for individual objects a statistical correction depending on the log axis ratio log R is applied. (12) The derived T - F relation for the DDO sample of late-type systems is in near perfect agreement in slope and zero point with the relation adopted by Bottinelli et al. for normal spiral galaxies of earlier types. The distance moduli derived from the 21-cm linewidths are in good statistical agreement with moduli derived from group membership and redshift but with a larger scatter. (13) The supergalactic anisotropy of the velocity-distance relation is in evidence in the DDO sample, confirming the departures from the ideal Hubble law indicated by earlier studies of brighter spiral galaxies. Publication: The Astronomical Journal Pub Date: June 1983 DOI: 10.1086/113365 Bibcode: 1983AJ.....88..764D Keywords: Dwarf Galaxies; H Lines; Magellanic Clouds; Ubv Spectra; Brightness Distribution; Centimeter Waves; Color; Distance; Hubble Diagram; Luminosity; Magnitude; Radial Velocity; Spectral Line Width; Spiral Galaxies; Astrophysics full text sources ADS | data products SIMBAD (243) NED (236)

view Abstract Citations (86) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio studies of the ionized gas in the nucleus of M 82. Seaquist, E. R. ; Bell, M. B. ; Bignell, R. C. Abstract Continuum and recombination-line radio observations of M82, obtained at 4.87 and 1.48 GHz using the VLA during July 1981 and January and September 1982 are reported. The data are presented in tables, graphs, maps and analyzed in combination with published radio and IR observations. A seven-layer model of the nuclear region is proposed, and the vertical gradient seen in the spectral index is attributed to an age gradient for the radiating particles and the 2000-km/s transport of relativistic particles out of the plane. The ionized gas in the central synchrotron-emission region is found to have maximum density 30/cu cm and to almost entirely fill the nuclear volume, while the molecular gas remains in small isolated clouds in pressure equilibrium with the ionized gas. The nature of the second component of M82, a compact H II complex apparently identical with the VLBI source 41.9 + 58 and objects seen in CO and the forbidden O I line at 63 microns, is briefly considered. Publication: The Astrophysical Journal Pub Date: July 1985 DOI: 10.1086/163322 Bibcode: 1985ApJ...294..546S Keywords: Galactic Nuclei; Galactic Structure; Hydrogen Clouds; Interstellar Gas; Ionized Gases; Radio Galaxies; Radio Spectra; Astronomical Models; Continuous Spectra; Infrared Astronomy; Line Spectra; Relativistic Electron Beams; Stellar Evolution; Synchrotron Radiation; Astrophysics full text sources ADS | data products SIMBAD (1) NED (1)

view Abstract Citations (78) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Rotation Curves for Spiral Galaxies in Clusters. II. Variations as a Function of Cluster Position Whitmore, Bradley C. ; Forbes, Duncan A. ; Rubin, Vera C. Abstract Rotation curves of spiral galaxies in clusters are examined using three criteria: (1) inner and outer velocity gradients; (2) residuals from synthetic rotation curves for field spirals; and (3) M/L gradients. A good correlation is found between the outer gradient of the rotation curve and the galaxy's distance from the center of the cluster, in the sense that the inner galaxies tend to have falling rotation curves, while the outer galaxies, and field galaxies, tend to have flat or rising rotation curves. A similar effect is seen in the residuals between the observed and synthetic rotation curves. A correlation is also found between the M/L gradient across a galaxy and the galaxy's position in the cluster, with the outer galaxies having steeper M/L gradients. An attempt to construct mass models produced inconclusive results. These correlations indicate that the inner cluster environment can strip away some fraction of the mass in the outer halo of a spiral galaxy or, alternatively, may not allow the halo to form. Publication: The Astrophysical Journal Pub Date: October 1988 DOI: 10.1086/166765 Bibcode: 1988ApJ...333..542W Keywords: Galactic Clusters; Galactic Evolution; Galactic Rotation; Galactic Structure; H I Regions; Spiral Galaxies; Correlation; Galactic Mass; Mass To Light Ratios; Morphology; Astrophysics; GALAXIES: CLUSTERING; GALAXIES: EVOLUTION; GALAXIES: INTERNAL MOTIONS; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (63) NED (52) Related Materials (1) Part 1: 1988ApJ...333..522R

In this paper we study consistent solutions of spherically symmetric space in metric f(R) gravity theory. Here we inversely obtain a generic action from metric solutions that describe flat rotation curves in spiral galaxies without dark matter. Then we show that obtained solutions are in conformity with Tully-Fisher relation and modified Newtonian dynamics, which are two strong constraints in justification of flat rotation curves in spiral galaxies.

Various theories, such as MOND, MOG, Emergent Gravity and theories avoid dark matter by assuming a change in General Relativity and/or in Newton's law. Galactic rotation curves are typically described well. Here the application to galaxy clusters is considered, focussed on the good lensing and X‐ray data for A1689. As a start, the no‐dark‐matter case is confirmed to work badly: the need for dark matter starts near the cluster centre, where Newton's law is still supposed to be valid. This leads to the conundrum discovered by Zwicky, which is likely only solvable in his way, namely by assuming additional (dark) matter. Neutrinos with eV masses serve well without altering the successes in (dwarf) galaxies.

This paper examines the crucial role dark matter plays in both the development of galactic structure and the timeline of cosmic evolution. First, it investigates how the masses of dark matter halos regulate the growth rate of supermassive black holes (SMBHs), thereby controlling galactic structure. The halo depth determines gas inflow rates and cooling efficiency, which decides the rate at which SMBHs accrete matter. As feedback from SMBHs in turn influences star formation rates and the stability of galactical structures, this paper discusses the specific outcomes each type of dark matter halo imposes on galactic structure. Then, the paper explores how different dark matter models, such as hot, cold, warm, and lambda cold dark matter, determine whether primordial density fluctuations survived or were erased during early phases of the universes history. The transfer function of each model is identified, then a graphic comparing each respective matter power spectrum, a cosmological parameter derived from the transfer function, is demonstrated. Finally, the paper would compare observational results from SDSS with the scenarios each matter power spectrum predicted and determine the most accurate dark matter model.

Dark-matter-only simulations predict that dark matter halos have cusp-like inner density profiles, while observations of low-mass galaxies have found a range of inner slopes that are typically much shallower. It is still not well established whether this discrepancy can be explained by baryonic feedback or if it may require modified dark matter models. To better understand the diversity of dark matter profiles in dwarf galaxies, we undertook a survey of 26 low-mass galaxies ( , v max = 50–140 km s−1) within 30 Mpc using the Palomar Cosmic Web Imager, which is among the largest integral field spectroscopic surveys of its type. In this paper, we derive Hα velocity fields for the full sample with a typical spatial resolution of ∼160 pc. We extract rotation curves and verify their robustness to several choices in the analysis. We present a method for improving the velocity precision obtained from image slicing spectrographs using narrowband Hα images. For 11 galaxies, we compare the Hα velocity fields to CO kinematics measured using CARMA, finding the maps to be in good agreement. The standard deviation of the difference is typically ∼7 km s−1, comparable to the level of turbulence in the interstellar medium, showing that the two tracers have substantially the same bulk kinematics. In a companion paper, we will use the rotation curves produced here to construct mass models of the galaxies and determine their dark matter density profiles.

view Abstract Citations (16) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Static structure of general relativistic, partially degenerate, self-gravitating, lepton configurations. I Numerical scheme Chau, W. Y. ; Lake, K. ; Stone, J. Abstract The Oppenheimer-Volkoff (1939) equations for isothermal, partially degenerate neutral lepton configurations have been solved numerically for arbitrary temperature and degree of degeneracy. For the specific case where the leptons are massive neutrinos (about 30 eV) with properties tightly constrained by cosmological considerations, it is found that it is possible to have a neutrino halo surrounding a normal galaxy with the right values of mass and radius required of the 'invisible halo' in the missing mass problem. The density distribution, however, yields a rotational curve which, with the present chosen values of parameters, does not fit the observations for spiral galaxies. Publication: The Astrophysical Journal Pub Date: June 1984 DOI: 10.1086/162129 Bibcode: 1984ApJ...281..560C Keywords: Density Distribution; Galactic Structure; Gravitational Fields; Leptons; Particle Density (Concentration); Relativistic Particles; Mass Distribution; Missing Mass (Astrophysics); Spiral Galaxies; Astrophysics full text sources ADS |

Physics instructors can enrich, enliven, and enhance their courses with conceptually rich cosmology content. In this paper, we specifically discuss how instructors can integrate lessons on Hubble’s law (as it relates to the expansion of the universe and dark energy) and spiral galaxies’ rotation curves (as they relate to the presence of dark matter) into an introductory, college-level course on mechanics. These cosmology topics intersect with the content of introductory physics in a number of areas, such as students’ abilities to read and interpret graphs and their conceptual understandings of both kinematics and dynamics. Throughout this paper, we draw upon the results from, and research-validated curricula informed by, physics and astronomy education research. In particular, we feature the results from a national study we recently completed with introductory college-level general education astronomy students on the teaching and learning of cosmology.

view Abstract Citations (33) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Computer-generated Galaxy Model with Long-lived Two-armed Spiral Structure Thomasson, Magnus ; Elmegreen, Bruce G. ; Donner, Karl Johan ; Sundelius, Bjorn Abstract A long-lived, two-armed spiral has been generated in an N-body computer simulation of a galaxy with a static bulge and halo and an active disk composed of 60,000 particles. The spiral lasts for about three pattern revolutions without severe distortion and persists for at least two more revolutions with distortions and bifurcations resulting from an increasingly clumpy interstellar medium. This suggests that two-armed grand design spirals in nonbarred, noninteracting galaxies can be long-lived if star formation and other heat sources not present in the simulation maintain a steady interstellar medium. The key factors contributing to the generation of this pattern are (1) a Q-barrier in the inner region, (2) a mass distribution and rotation curve that allows swing amplification of m = 2 waves with an inner Lindblad resonance inside the Q-barrier, (3) a star- cooling routine that keeps the stellar velocity dispersion constant with adiabatic variations allowed, and (4) a substantial amount of cold, dissipating gas in the disk. The stellar pattern extends from the Q-barrier to the outer Lindblad resonance, and the gaseous pattern extends from the region of the inner Lindblad resonance to the outer Lindblad resonance. Publication: The Astrophysical Journal Pub Date: June 1990 DOI: 10.1086/185739 Bibcode: 1990ApJ...356L...9T Keywords: Astronomical Models; Computerized Simulation; Galactic Evolution; Galactic Structure; Spiral Galaxies; Disk Galaxies; Galactic Bulge; Interstellar Matter; Many Body Problem; Astrophysics; GALAXIES: EVOLUTION; GALAXIES: STRUCTURE full text sources ADS |